132 LIFE OF opinion that the southern animals had wandered too far north into higher latitudes in hot summers— especially In former ages, when, by the greater volcanic activity of the then hotter earth, those north- ern regions, also, must have had a higher tempera- ture—that they had been suddenly overtaken by the winter, and had been buried in ico which haw not melted since that time; and that inundations of rivei'S, flowing northward, on whose shores numerous remains of southern animals may yet be found, may hayo washed them towards the north. Humboldt also acknowledged the direction of the winds and tides, as one modifying cause of the cli- mate prevailing over certain large portions of land, and these again stand in intimate relation to the form of the continent, and often divert the isotltermic lines considerably from their regular course. This ex- plained, clearly, how two countries or districts lying under the same degree of latitude, but at a great dis- tance from each other, could have two entirely cUftb- rent climates.* Humboldt showed how the revolu- tion of the earth on its axis must caxise the great current of the waters of the ocean to flow from east to west, and that this current must be the strongest at the greatest peripherium of the earth, beneath the equator; that another current from the poles towards the greatest peripherium, must necessarily co-exist, which must flow from the north pole, first towards the south, and then westward, following the chief current. The cold waters coming from the polar circles there- fore, wash the eastern shores of the countries of the earth, while the heated waters, flowing back from the equator, beat against the western coasts. The pre- vailing winds blow analogously with these ocean tides; and hence the coldness of the eastern, and the warmth of the western coasts, are self-evident. We "* * These theories of Humboldt HaTe been worked out by Solicitw and Dowe, wlio have founded many important facts on this banla.